JP2006186337A - Light emitting element and electronic apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element in which a drive voltage is low, reliability is high, which can prevent the short circuit of electrodes, and can give high extraction efficiency of the light and high hole-injecting or hole-transporting, and also to provide an electronic apparatus using it. <P>SOLUTION: A conjugate molecule with small ionization potential and a substance with electronic acceptance to the conjugate molecule are mixed to form a complex. A compound layer which constitutes an element is formed using the complex as an element material. The compound layer is arranged between the first electrode and the light emitting layer or between the second electrode and the light emitting layer. Since the compound layer has high conductivity, even if the film is thick, the drive voltage does not rise. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting device. In particular, the present invention relates to a light-emitting element having a layer formed of a complex of a conjugated molecule and a substance having an electron accepting property with respect to the conjugated molecule. Further, the present invention relates to a light emitting device having a light emitting element.

  An electroluminescence (EL) display is one of the most attracting attention as a next-generation flat panel display element, and is composed of a light emitting element. In the light-emitting element, when current is passed, electrons injected from the cathode and holes injected from the anode are recombined in the light-emitting layer to form molecular excitons. The light-emitting element emits light using photons emitted when the molecular excitons return to the ground state. Therefore, using all of the excitation energy of molecular excitons for light emission is one of the conditions for manufacturing a light-emitting element with high emission efficiency.

  One example of satisfying the above condition is a stacked structure of light emitting elements. For example, a stacked layer is formed with a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, or the like between a pair of electrodes including an anode and a cathode.

  In addition, efficient injection of holes and electrons as carriers into the light-emitting layer is one of the conditions for manufacturing a light-emitting element with high light-emission efficiency. Therefore, it is known that a material having a low ionization potential is used for the hole injection layer and a material having a high electron affinity is used for the electron injection layer.

  The layers constituting the stacked structure of the light-emitting element as described above are formed of a metal oxide that is an inorganic compound or an organic compound.

In addition, attempts have been made to form a light emitting element using a layer in which an organic compound and an inorganic compound are mixed. For example, in Patent Document 1 below, a light-emitting element formed by laminating a layer made of a material in which an organic compound (a hole transporting compound, an electron transporting compound, or a light-emitting compound) is dispersed in a silica matrix via a covalent bond is also disclosed. It is disclosed. In patent document 1, it is reported that durability and heat resistance of an element improve.
JP 2000-306669 A

  However, when a metal oxide is used as a layer constituting the light emitting element, there are the following problems. Metal oxide is easily crystallized, and unevenness is formed on the surface of the metal oxide by crystallization. An electric field was concentrated on the convex portion, and a highly reliable light-emitting element could not be obtained. In addition, when the metal oxide film is thickened for the purpose of preventing short-circuit between electrodes of the light-emitting element due to dust or the like, or for the purpose of optical design to efficiently extract light from the light-emitting layer, the driving voltage increases. There was a problem.

  On the other hand, when an organic compound is used as a layer constituting the light emitting element, if an anode having a small work function is used, holes are less likely to enter the organic compound, and the drive voltage increases. Therefore, it is not preferable to use a material having a small work function as the anode, and the anode material is limited. Further, like the metal oxide material, there is a problem that the drive voltage increases when the film thickness is increased.

  Further, in the light-emitting element disclosed in Patent Document 1, since an organic compound is simply dispersed in an insulating metal oxide, current does not easily flow compared to a conventional light-emitting element. (That is, the voltage required to pass a certain current increases). That is, only a low density current flows. Therefore, even if durability and heat resistance are obtained, the configuration of Patent Document 1 causes an increase in driving voltage and an accompanying increase in power consumption.

  Furthermore, when the film thickness is increased with the configuration shown in Patent Document 1, the increase in the driving voltage becomes more obvious. That is, in the configuration of Patent Document 1, it is practically difficult to increase the film thickness.

  FIG. 14 shows a conventional light-emitting element disclosed in Patent Document 1, in which an organic compound is dispersed in a silica matrix between a first electrode (anode) 1501 and a second electrode (cathode) 1502. A layer 1503 is sandwiched. That is, the layer 1503 is entirely composed of a silica matrix, but 1511 is a hole transport layer made of a material in which a hole transport compound is dispersed in a silica matrix, and 1513 is an electron transport compound dispersed in a silica matrix. An electron transport layer made of a material, and 1512 is a light emitting layer made of a material in which a light emitting compound is dispersed in a silica matrix. When voltage is applied to this element, holes are injected from the first electrode (anode) 1501 and electrons are injected from the second electrode (cathode) 1502, recombined in the light-emitting layer 1512, and the light-emitting compound emits light. It is thought that.

  Carrier transport in this element is carried out by the hole transport layer 1511 and the electron transport layer 1513. However, since an organic compound is dispersed in an insulating silica matrix, there is a problem that current hardly flows. For example, in the hole transport layer 1511, since holes move by hopping between hole transport compounds existing in the hole transport layer 1511, the insulating silica matrix is involved in hole transport. There is no. Conversely, hole hopping is hindered. The same can be said for the electron transport layer 1513. Therefore, as a matter of course, the driving voltage increases even when compared with the conventional light emitting device.

  Therefore, an object of the present invention is to provide a light emitting element with a low driving voltage. It is another object to provide a light-emitting element with high reliability. It is another object of the present invention to provide a light emitting element that can easily prevent a short circuit between electrodes. Another object is to provide a light-emitting element with high light extraction efficiency. It is another object of the present invention to provide a light-emitting element having a high hole-injecting property or a high hole-transporting property.

  As a result of intensive studies, the inventor has made electron acceptability to any one of the conjugated molecules represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5] (hereinafter referred to as conjugated molecules) and this conjugated molecule. A layer (hereinafter referred to as a composite layer) composed of a complex with a substance (hereinafter referred to as an electron-accepting material) is provided between at least one of the pair of electrodes and a light emitting layer positioned between the pair of electrodes. It was found that the problem can be solved by arranging.

  As the electron-accepting substance, a metal oxide or a metal nitride is preferable, and a transition metal oxide of any of Groups 4 to 12 of the periodic table is more preferable. Among them, many transition metal oxides of Groups 4 to 8 of the periodic table have high electron-accepting properties, and in particular, vanadium oxide, molybdenum oxide, rhenium oxide, tungsten oxide, ruthenium oxide, titanium oxide, and chromium oxide. Zirconium oxide, hafnium oxide, tantalum oxide and niobium oxide are preferred.

Further, an organic compound having an electron accepting property may be used as the electron accepting substance. Specific examples include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (F4-TCNQ) and chloranil. Further, a Lewis acid may be used as the electron accepting substance. Examples of Lewis acid include FeCl ₃ (iron chloride (III)) and AlCl ₃ (aluminum chloride).

  In addition, the optimum mixing ratio of the electron-accepting substance in the composite layer and any of the conjugated molecules represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5] is as follows. 1-10, preferably 0.5-2. At this mixing ratio, electrons are efficiently exchanged between the electron-accepting substance and the conjugated molecule, and the conductivity of the composite layer is the highest.

（式中、ＸとＺは同一または異なっており、且つ、ＸとＺはそれぞれ硫黄原子、酸素原子、水素、アルキル基もしくはアリール基が結合した窒素原子、又は水素、アルキル基もしくはアリール基が結合した珪素原子のいずれかであり、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかである。）

(Wherein X and Z are the same or different, and X and Z are each a nitrogen atom to which a sulfur atom, oxygen atom, hydrogen, alkyl group or aryl group is bonded, or a hydrogen, alkyl group or aryl group bonded thereto) Y is an arylene group, and R ¹ to R ⁶ are each a hydrogen atom, an aryl group, an alkyl group, a cyano group, a dialkylamino group, a thioalkoxy group, or an alkoxy group. is there.)

（式中、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかである。）

(In the formula, Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, a thioalkoxy group, or an alkoxy group.)

（式中、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかである。）

(In the formula, Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, a thioalkoxy group, or an alkoxy group.)

（式中、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかであり、Ｒ^７とＲ^８は水素、アルキル基又はアリール基のいずれかである。）

(Wherein Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, aryl group, alkyl group, cyano group, dialkylamino group, thioalkoxy group, or alkoxy group, and R ⁷ and R ⁸ is either hydrogen, an alkyl group or an aryl group.)

（式中、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかであり、Ｒ^７からＲ^１０はそれぞれ水素、アルキル基又はアリール基のいずれかである。）

(In the formula, Y is an arylene group, each R ⁶ is from R ^1, hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, or a thioalkoxy group, or an alkoxy group, a R ⁷ Each R ¹⁰ is hydrogen, an alkyl group, or an aryl group.)

  In the conjugated molecules represented by the above general formulas [Chemical Formula 1] to [Chemical Formula 5], Y is an arylene group and a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or oxygen, nitrogen, A divalent heteroaromatic group having 4 to 30 carbon atoms and containing sulfur or silicon.

In the conjugated molecules represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5], R ¹ and R ² form a ring structure, and R ³ and R ⁴ form a ring structure.

  One of the structures of the present invention includes a pair of electrodes including a first electrode and a second electrode, a light emitting layer between the electrodes, and a first electrode between the first electrode and the light emitting layer. And a second layer between the second electrode and the light-emitting layer. The first layer or the second layer includes an electron-accepting substance and the general formulas [Chemical Formula 1] to [Chemical Formula 5]. A composite layer with any of the conjugated molecules represented by

  In the above structure, the composite layer may be disposed in contact with the first electrode in the first layer, or may be disposed in contact with the light emitting layer. In the second layer, the composite layer may be disposed in contact with the second electrode or may be disposed in contact with the light emitting layer.

  In the above structure, the first layer and the second layer may include a composite layer. In a light-emitting element that emits light from a light-emitting layer when a voltage is applied to the electrode so that the potential of the first electrode is higher than the potential of the second electrode, the second layer includes a composite layer. Provides an electron generating layer on the light emitting layer side in contact with the composite layer.

  The composite layer in this specification is formed using a composite of any of the conjugated molecules represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5] described above and a substance having an electron accepting property with respect to the conjugated molecule. It is a layer that has been.

Conjugated molecules represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5] have two skeletons from any one of a thiophene skeleton, a furan skeleton, a pyrrole skeleton, and a silole skeleton, which are electron-rich aromatic rings having a small ionization potential. It is introduced into a conjugated molecule such as a ring. Therefore, it is known that the conjugated molecule has a small ionization potential. In particular, when R ¹ to R ⁶ are electron donating substituents such as an alkoxy group, the conjugated molecule has a smaller ionization potential. By mixing such a conjugated molecule and an electron-accepting substance to form a composite layer, electrons are transferred between the conjugated molecule and the electron-accepting substance. That is, before the voltage is applied to the light-emitting element, holes are already generated in the composite layer based on the ionization potential of the conjugated molecule.

  Therefore, it is possible to obtain a light-emitting element with a reduced hole injection barrier by having the composite layer of the present application rather than a layer using only a material having a low ionization potential. In addition, a light-emitting element in which holes can move more easily can be obtained. In view of the function of such a composite layer, the composite layer of the present application may function like a hole generation layer and a hole transport layer.

  In addition, as described above, in the composite layer used in the present application, electrons are transferred even before voltage application, and thus the composite layer is a highly conductive film. Therefore, a light-emitting element with low driving voltage and power consumption can be provided. In addition, the drive voltage rarely increases in proportion to the increase in the thickness of the composite layer. Therefore, the composite layer can be thickened to prevent a short circuit between the electrodes of the light emitting element. Further, the light extraction efficiency can be optimized by increasing the thickness of the composite layer. Furthermore, a highly reliable light-emitting element can be provided. In addition, a light-emitting element with high emission efficiency can be provided.

  Further, since a composite layer in which a conjugated molecule and an electron-accepting substance are mixed is difficult to crystallize, a light-emitting element with less malfunction due to crystallization of the layer can be obtained.

  Hereinafter, one embodiment of the present invention will be described. However, the present invention can be implemented in many different modes within a practicable range. It will be readily appreciated by those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, the present invention is not construed as being limited to the description of the embodiment. Further, the following embodiments and examples can be combined as appropriate.

(Embodiment 1)
One mode of a light-emitting element of the present invention will be described with reference to FIG.

  1A to 1C, a first layer 111 in contact with the first electrode 101 and a second layer in contact with the first layer 111 between the first electrode 101 and the second electrode 102 are illustrated. A light-emitting element having the first layer 112, the second layer 112, and the third layer 113 in contact with the second electrode 102 is shown. In FIG. 1, light is emitted when a voltage is applied to the electrode such that the potential of the first electrode 101 is higher than the potential of the second electrode 102. The second layer 112 is a light emitting layer, and the third layer 113 is a layer having a function of carrying or injecting electrons to the light emitting layer which is the second layer.

  The second layer 112 includes a light emitting material. The second layer 112 may be a layer formed only from a light emitting substance. However, in the case where concentration quenching occurs, it is preferable that the layer be mixed so that the light-emitting substance is dispersed in a layer made of a substance having an energy gap larger than that of the light-emitting substance. By including a light-emitting substance in the second layer 112 in a dispersed manner, light emission can be prevented from being quenched due to concentration. Here, the energy gap refers to an energy gap between the LUMO level and the HOMO level.

There is no particular limitation on the light-emitting substance, and a substance that has favorable emission efficiency and can emit light with a desired emission wavelength may be used. For example, to obtain red light emission, 4-dicyanomethylene-2-isopropyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] -4H-pyran ( Abbreviation: DCJTI), 4-dicyanomethylene-2-methyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] -4H-pyran (abbreviation: DCJT), 4 -Dicyanomethylene-2-tert-butyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] -4H-pyran (abbreviation: DCJTB), periflanthene, 2,5 -Dicyano-1,4-bis [2- (10-methoxy-1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] benzene, etc., emission spectrum from 600 nm to 680 nm Substance which exhibits emission with a peak can be used as a light-emitting substance. When green light emission is desired, N, N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin 545T, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), etc., emits light from 500 nm to 550 nm. A substance that emits light having a spectral peak can be used as the light-emitting substance. When blue light emission is desired, 9,10-bis (2-naphthyl) -tert-butylanthracene (abbreviation: t-BuDNA), 9,9′-bianthryl, 9,10-diphenylanthracene (abbreviation) : DPA), 9,10-bis (2-naphthyl) anthracene (abbreviation: DNA), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-gallium (abbreviation: BGaq), bis (2-methyl) A substance exhibiting light emission having an emission spectrum peak at 420 nm to 500 nm, such as -8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), can be used as the light-emitting substance. As described above, in addition to a substance that emits fluorescence, bis [2- (3,5-bis (trifluoromethyl) phenyl) pyridinato-N, C ^{2 ′} ] iridium (III) picolinate (abbreviation: Ir (CF ₃ ppy) ₂ (pic)), bis [2- (4,6-difluorophenyl) pyridinato-N, C ^{2 ′} ] iridium (III) acetylacetonate (abbreviation: FIr (acac)), bis [2- (4 , 6-Difluorophenyl) pyridinato-N, C ^{2 ′} ] iridium (III) picolinate (abbreviation: FIr (pic)), tris (2-phenylpyridinato-N, C ^{2 ′} ) iridium (abbreviation: Ir (ppy) ₃ ) A phosphorescent substance such as ₃ ) can also be used as the light emitting substance.

Further, there is no particular limitation on a substance that is included in the light-emitting layer together with the light-emitting substance and is used for dispersing the light-emitting substance, and may be appropriately selected in consideration of an energy gap of the substance used as the light-emitting substance. For example, anthracene derivatives such as 9,10-di (2-naphthyl) -2-tert-butylanthracene (abbreviation: t-BuDNA), or 4,4′-bis (N-carbazolyl) biphenyl (abbreviation: CBP) Carbazole derivatives of 2,3-bis (4-diphenylaminophenyl) quinoxaline (abbreviation: TPAQn), 2,3-bis {4- [N- (1-naphthyl) -N-phenylamino] phenyl} -dibenzo [ In addition to quinoxaline derivatives such as f, h] quinoxaline (abbreviation: NPDiBzQn), bis [2- (2-hydroxyphenyl) pyridinato] zinc (abbreviation: Znpp ₂ ), bis [2- (2-hydroxyphenyl) benzoxazola G] A metal complex such as zinc (abbreviation: ZnBOX) or the like can be used together with a light-emitting substance.

  In FIG. 1A, the first layer 111 includes a composite layer 114 and a hole transport layer 115 which are formed using a composite of a conjugated molecule and an electron-accepting substance. The composite layer 114 is disposed on the first electrode 101 side in the first layer, and the hole transport layer 115 is disposed on the second layer 112 side. In this configuration, the composite layer 114 functions as a hole generation layer.

  In general, an electrode material having a high work function is used for the first electrode 101. However, when the composite layer 114 and the first electrode 101 are in contact with each other, the first electrode 101 is an electrode having a low work function. (For example, aluminum or magnesium) can be used. This is because the ionization potential of the conjugated molecule, which is a constituent factor of the composite layer 114, is very small, and holes are generated in the composite layer 114. Therefore, the first electrode 101 and the composite layer 114 having a small work function This is because holes are also exchanged between them.

  In FIG. 1B, the first layer 111 includes a composite layer 116 and a hole-injection layer 117 that are formed using a composite of a conjugated molecule and an electron-accepting substance. The composite layer 116 is disposed on the second layer side in the first layer, and the hole injection layer 117 is disposed on the first electrode 101 side. In this configuration, the composite layer 116 functions as a hole transport layer.

  In FIG. 1C, the first layer 111 is a composite layer 118 including a composite made of a conjugated molecule and an electron accepting substance. In this structure, the composite layer 118 functions as a hole generation layer, a hole transport layer, or a hole generation layer and a hole transport layer.

  1A to 1C, since the composite layer is located between the first electrode 101 and the second layer 112 which is a light-emitting layer, hole injecting property or hole transporting property is achieved. A light emitting element having a high value can be obtained. Further, since the composite layer has high conductivity, the driving voltage does not increase even when the film thickness is increased. Therefore, the composite layer can be thickened to optimize the light extraction efficiency, and the short circuit between the electrodes of the light emitting element can be suppressed. Note that in each of FIGS. 1A and 1B, an example in which the composite layer is in contact with the first electrode or the second layer is described; however, the composite layer is not necessarily in contact. 1A, there may be another layer between the composite layer 114 and the first electrode 101. In FIG. 1B, another layer may be provided between the composite layer 116 and the second layer 112. There may be layers.

In FIG. 1A, the hole transport layer 115 is a layer having a function of transporting holes, and has a function of transporting holes from the composite layer 114 to the second layer 112. By providing the hole transport layer 115, the distance between the composite layer 114 and the second layer 112 can be increased, and as a result, light emission is quenched due to the metal contained in the composite layer 114. Can be prevented. The hole transport layer is preferably formed using a substance having a high hole transport property, and particularly preferably formed using a substance having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher. Note that a substance having a high hole-transport property has a higher hole mobility than an electron, and the ratio of the hole mobility to the electron mobility (= hole mobility / electron mobility) is 100. Larger than the substance. Specific examples of a substance that can be used for forming the hole-transport layer 115 include 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB), 4, 4′-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl (abbreviation: TPD), 4,4 ′, 4 ″ -tris (N, N-diphenylamino) triphenylamine (abbreviation: TDATA), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (abbreviation: MTDATA), 4,4′-bis {N- [4- ( N, N-di-m-tolylamino) phenyl] -N-phenylamino} biphenyl (abbreviation: DNTPD), 1,3,5-tris [N, N-di (m-tolyl) amino] benzene (abbreviation: m -MTDAB), 4,4 ', 4''- Squirrel (N- carbazolyl) triphenylamine (abbreviation: TCTA), phthalocyanine _{(abbreviation:} H 2 Pc), copper phthalocyanine (abbreviation: CuPc), or vanadyl phthalocyanine (abbreviation: VOPc), and the like.

In FIG. 1B, the hole injection layer 117 is a layer having a function of assisting injection of holes from the first electrode 101 to the composite layer 116. By providing the hole injection layer 117, the difference in ionization potential between the first electrode 101 and the composite layer 116 is reduced, and holes are easily injected. The hole injection layer 117 has a lower ionization potential than the material forming the composite layer 116 and has a higher ionization potential than the material forming the first electrode 101, or the composite layer 116 and the first layer. It is preferable to use a substance whose energy band is bent when it is provided as a 1 to 2 nm thin film between the electrode 101 and the electrode 101. Specific examples of a substance that can be used to form the hole-injection layer 117 include phthalocyanine-based compounds such as phthalocyanine (abbreviation: H ₂ Pc) and copper phthalocyanine (CuPC), or poly (ethylenedioxythiophene) / Examples thereof include a polymer such as a poly (styrenesulfonic acid) aqueous solution (PEDOT / PSS). It is preferable to form the hole injection layer 117 so that the ionization potential in the hole injection layer 117 is relatively larger than the ionization potential in the composite layer 116. Note that in the case where the hole-injection layer 117 is provided, the first electrode 101 is preferably formed using a substance having a high work function such as indium tin oxide.

The third layer 113 may be any layer as long as it has a function of carrying or injecting electrons injected from the second electrode 102 to the light-emitting layer that is the second layer, and the structure thereof is not limited. When the third layer 113 includes, for example, an electron transport layer, the electron transport layer may be anything as long as it generally has a function of transporting electrons. As a material for forming the electron transport layer, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Almq ₃ ), bis (10-hydroxybenzo [h ] - quinolinato) beryllium (abbreviation: BeBq _2), bis (2-methyl-8-quinolinolato) -4-phenylphenolato - aluminum (abbreviation: BAlq), bis [2- (2-hydroxyphenyl) benzoxazolato ] In addition to metal complexes such as zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ), 2- (4-biphenylyl) -5 -(4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5- (p -Tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (abbreviation: OXD-7), 3- (4-tert-butylphenyl) -4-phenyl-5- (4- Biphenylyl) -1,2,4-triazole (abbreviation: TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2,4- Triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), 4,4-bis (5-methylbenzoxazol-2-yl) stilbene (abbreviation: BzOs), and the like It is done.

Alternatively, the electron transport layers of the hole transport layer 115 and the third layer 113 may be formed using a bipolar substance. A bipolar substance is the ratio of the mobility of one carrier to the mobility of the other carrier when the mobility of one of the electrons or holes is compared with the mobility of the other carrier. A substance whose value is 100 or less, preferably 10 or less. As a bipolar substance, for example, 2,3-bis (4-diphenylaminophenyl) quinoxaline (abbreviation: TPAQn), 2,3-bis {4- [N- (1-naphthyl) -N-phenylamino] phenyl } -Dibenzo [f, h] quinoxaline (abbreviation: NPDiBzQn) and the like. Among bipolar substances, it is particularly preferable to use a substance having a hole and electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or more. Alternatively, the hole transport layer 115 and the electron transport layer may be formed using the same bipolar substance.

When the third layer 113 includes an electron generation layer, the electron generation layer may be any layer as long as it generally has a function of generating electrons. The electron generating layer can be formed by mixing at least one substance selected from a substance having a high electron transporting property and a bipolar substance and a substance exhibiting an electron donating property to these substances. Here, among substances having a high electron transporting property and bipolar substances, a substance having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or more is particularly preferable. As the substance having a high electron transporting property and the bipolar substance, those described above can be used, respectively. Moreover, as the substance exhibiting electron donating property, a substance selected from alkali metals and alkaline earth metals, specifically, lithium (Li), calcium (Ca), sodium (Na), potassium (K), Magnesium (Mg) or the like can be used. Further, alkali metal oxides or alkaline earth metal oxides, alkali metal nitrides, alkaline earth metal nitrides, alkali metal fluorides, alkaline earth metal fluorides, etc., specifically lithium oxide (Li ₂ O ), Calcium oxide (CaO), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), magnesium oxide (MgO), magnesium nitride (Mg ₃ N ₂ ), lithium fluoride (LiF), At least one substance selected from cesium fluoride (CsF), calcium fluoride (CaF ₂ ), and the like can also be used as the substance exhibiting electron donating properties.

  The first electrode 101 includes indium tin oxide, indium tin oxide containing silicon oxide, indium oxide containing 2 to 20 wt% zinc oxide, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or a material having a high work function such as tantalum nitride. it can.

  For the second electrode 102, in addition to indium tin oxide, indium tin oxide containing silicon oxide, indium oxide containing 2 to 20 wt% zinc oxide, gold (Au), platinum (Pt), nickel ( Using a material having a high work function such as Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), and tantalum nitride. It may be formed using a substance having a low work function such as aluminum or magnesium.

  The light-emitting element described in this embodiment can be stacked in order from the first electrode or the second electrode by using a known film formation method. In particular, the composite layer can be formed by evaporating both the conjugated molecule and the electron accepting substance by resistance heating and co-evaporating. In addition, while the conjugated molecule is evaporated by resistance heating, the electron accepting substance may be evaporated by electron beam (EB) and co-evaporated. Further, there is a method in which the conjugated molecules are evaporated by resistance heating, and at the same time, an electron accepting substance is sputtered and both are deposited simultaneously. In addition, the film may be formed by a wet method.

  Similarly, the first electrode 101 and the second electrode 102 can be formed by a resistance heating evaporation method, EB evaporation, sputtering, a wet method, or the like.

  In the case where the second electrode 102 was formed in order and the first electrode 101 was formed by sputtering, there was sputtering damage to the layer located under the first electrode. However, since the composite layer is harder than the organic film, the structure shown in FIGS. 1A and 1C is less susceptible to sputter damage and serves as a protective film that protects the light-emitting layer from sputter damage. Thereby, a light-emitting element with few defects can be obtained.

(Embodiment 2)
This embodiment will be described with reference to FIG.

  In FIG. 2, a first layer 211 in contact with the first electrode 201, a second layer 212 in contact with the first layer 211, and a second layer between the first electrode 201 and the second electrode 202. A light-emitting element having 212 and a third layer 213 in contact with the second electrode 202 is shown. The light-emitting element in FIG. 2 emits light when a voltage is applied so that the potential of the first electrode 201 is higher than the potential of the second electrode 202. The second layer 212 is a light-emitting layer, and the first layer 211 is a layer having a function of transporting or injecting holes to the light-emitting layer that is the second layer. The first layer may have a hole injection layer or a hole transport layer. As the light-emitting material, the first and second electrode materials, the electron transporting material, the hole transporting material, and the hole injecting material of this embodiment, the materials described in Embodiment Mode 1 can be used.

  The third layer 213 includes a composite layer 214 on the second electrode 202 side and an electron generation layer 215 on the second layer 212 side. Between the electron generating layer 215 and the second layer 212, a layer such as an electron transporting layer may be interposed or may not be interposed.

The electron generating layer 215 can be formed by mixing at least one substance selected from a substance having a high electron transporting property and a bipolar substance and a substance showing an electron donating property with respect to these substances. Here, among substances having a high electron transporting property and bipolar substances, a substance having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or more is particularly preferable. As the substance having a high electron transporting property and the bipolar substance, those described above can be used, respectively. Moreover, as the substance exhibiting electron donating property, a substance selected from alkali metals and alkaline earth metals, specifically, lithium (Li), calcium (Ca), sodium (Na), potassium (K), Magnesium (Mg) or the like can be used. Alkali metal oxides or alkaline earth metal oxides, alkali metal nitrides, alkaline earth metal nitrides, alkali metal fluorides, alkaline earth metal fluorides, etc., specifically lithium oxides (Li ₂ O), calcium oxide (CaO), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), magnesium oxide (MgO), magnesium nitride (Mg ₃ N ₂ ), lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ₂ ), or the like can also be used as a substance exhibiting electron donating properties.

  With the structure of this embodiment mode, the composite layer 214 can be provided between the second layer 212 that is a light-emitting layer and the second electrode 202. Since the composite layer 214 is a highly conductive film, the thickness of the composite layer can be increased, whereby a short circuit between electrodes can be prevented and a light-emitting element with high light extraction efficiency can be obtained. In addition, since the composite layer is difficult to crystallize, a light-emitting element with less malfunction due to crystallization of the layer can be obtained.

  Note that the practitioner may appropriately select whether to provide a hole transport layer in the first layer 211 or an electron transport layer between the electron generation layer 215 and the second layer 212. For example, when there is no problem such as quenching due to metal without providing a hole transport layer and an electron transport layer, these layers are not necessarily provided.

  The light-emitting element described in this embodiment can be formed by a known film formation method in a manner similar to the manufacturing method described in Embodiment 1.

  When the first electrode 201 was deposited in order and the second electrode 202 was deposited by sputtering, there was sputtering damage to the layer located under the second electrode. However, since the composite layer 214 is harder than the organic film, it is less susceptible to sputter damage and serves as a protective film that protects the light emitting layer from sputter damage. Thereby, a light-emitting element with few defects can be obtained.

(Embodiment 3)
In this embodiment mode, the stacked structure between the second layer 112 and the first electrode 101 shown in Embodiment Mode 1, and the second layer 212 and the second electrode 202 shown in Embodiment Mode 2 are used. Is a combination of the laminated structures between the two.

  In this case, a composite layer is disposed between the first electrode and the light-emitting layer and between the second electrode and the light-emitting layer, respectively, so that the conductivity is higher and the hole injectability or hole transport is higher. A light-emitting element with high performance can be provided. That is, a light emitting device having the advantages of the first embodiment and the advantages of the second embodiment can be obtained.

  A light-emitting element which is one embodiment of this embodiment is illustrated in FIG. 3A to 3C, a second layer 312 that is a light-emitting layer is provided between a first electrode 301 that is a pair of electrodes and a second electrode 302, and the first electrode 301 is used. The first layer 311 is disposed between the second electrode 312 and the second layer 312, and the third layer 313 is disposed between the second electrode 302 and the second layer 312. The third layer includes a first composite layer 324 on the second electrode 302 side and an electron generation layer 325 on the second layer 312 side. The element illustrated in FIG. 3 is a light-emitting element that emits light when a voltage is applied to an electrode so that the potential of the first electrode 301 is higher than the potential of the second electrode 302.

  FIG. 3A shows a structure combining FIG. 1A and FIG. The first layer 311 in FIG. 3A includes a hole transport layer 326 on the second layer 312 side and a second composite layer 327 on the first electrode 301 side.

  FIG. 3B shows a structure combining FIG. 1B and FIG. The first layer 311 in FIG. 3B includes a second composite layer 328 on the second layer side and a hole injection layer 329 on the first electrode 301 side.

  FIG. 3C shows a structure combining FIG. 1C and FIG. The first layer 311 in FIG. 3C is a second composite layer 330.

  In this embodiment, the complex of the conjugated molecule and the electron-accepting substance constituting the first composite layer and the second composite layer may be the same or different. In the light-emitting element of this embodiment, a composite layer can be provided in both the first layer 311 and the third layer 313; thus, the light-emitting element has high conductivity and high light extraction efficiency. In addition, when the first electrode or the second electrode is formed by sputtering, there is a problem of sputtering damage to a layer located in a lower layer. However, in the structure shown in FIGS. 3A and 3C, a composite layer is formed in contact with the first electrode and the second electrode, so that the sputter accompanying the formation of the first electrode or the second electrode. Damage can be prevented.

  In FIG. 3, the electron transport layer is not provided between the electron generation layer 325 and the second layer 312, but the practitioner may select appropriately whether or not to provide it.

(Embodiment 4)
The light-emitting element of the present invention can be used for a pixel of a display device or as a light source. In the case where a light emitting element is used for a pixel, an image with good display color can be displayed without malfunction. In addition, a highly reliable display device or light-emitting device can be provided. In addition, when a light-emitting element is used as a light source, a bright light-emitting device can be obtained with less defects due to malfunction of the light-emitting element.

  In this embodiment mode, a light-emitting device which has the light-emitting element of the present invention in a pixel and has a display function will be described.

  FIG. 4 is a schematic view of the light emitting device as viewed from above. In FIG. 4, over a substrate 6500, a pixel portion 6511 using the light emitting element of the present invention, a source signal line driver circuit 6512, a write gate signal line driver circuit 6513, and an erase gate signal line driver circuit 6514 are provided. And are provided. The source signal line driver circuit 6512, the writing gate signal line driver circuit 6513, and the erasing gate signal line driver circuit 6514 are respectively FPC (flexible printed circuit) 6503 which is an external input terminal through a wiring group. Connected. The source signal line driver circuit 6512, the writing gate signal line driver circuit 6513, and the erasing gate signal line driver circuit 6514 receive a video signal, a clock signal, a start signal, a reset signal, and the like from the FPC 6503, respectively. . A printed wiring board (PWB) 6504 is attached to the FPC 6503. Note that the driver circuit portion is not necessarily provided over the same substrate as the pixel portion 6511 as described above. For example, an IC chip mounted on an FPC on which a wiring pattern is formed (TCP) or the like is used. It may be used and provided outside the substrate.

  In the pixel portion 6511, a plurality of source signal lines extending in the column direction are arranged side by side in the row direction. In addition, current supply lines are arranged side by side in the row direction. In the pixel portion 6511, a plurality of gate signal lines extending in the row direction are arranged side by side in the column direction. In the pixel portion 6511, a plurality of pixel circuits including light-emitting elements as described in Embodiments 1 to 3 are arranged.

  FIG. 5 is a diagram showing a circuit for operating one pixel. The circuit shown in FIG. 5 includes a first transistor 901, a second transistor 902, and a light emitting element 903 of the present invention.

  Each of the first transistor 901 and the second transistor 902 is a three-terminal element including a gate electrode, a drain region, and a source region, and has a channel region between the drain region and the source region. Here, since the source region and the drain region vary depending on the structure and operating conditions of the transistor, it is difficult to limit which is the source region or the drain region. Therefore, in this embodiment, regions functioning as a source or a drain are referred to as a first electrode and a second electrode, respectively.

  The gate signal line 911 and the writing gate signal line driving circuit 913 are provided so as to be electrically connected or disconnected by a switch 918. The gate signal line 911 and the erasing gate signal line driver circuit 914 are provided so as to be electrically connected or disconnected by a switch 919. The source signal line 912 is provided so as to be electrically connected to either the source signal line driver circuit 915 or the power source 916 by the switch 920. The gate of the first transistor 901 is electrically connected to the gate signal line 911. The first electrode of the first transistor 901 is electrically connected to the source signal line 912, and the second electrode is electrically connected to the gate electrode of the second transistor 902. The first electrode of the second transistor 902 is electrically connected to the current supply line 917, and the second electrode is electrically connected to one electrode included in the light-emitting element 903. Note that the switch 918 may be included in the write gate signal line driver circuit 913. The switch 919 may also be included in the erase gate signal line driver circuit 914. Further, the switch 920 may also be included in the source signal line driver circuit 915.

  There is no particular limitation on the arrangement of transistors, light-emitting elements, and the like in the pixel portion, but they can be arranged as shown in the top view of FIG. In FIG. 6, the first electrode of the first transistor 1001 is connected to the source signal line 1004, and the second electrode is connected to the gate electrode of the second transistor 1002. The first electrode of the second transistor 1002 is connected to the current supply line 1005, and the second electrode is connected to the electrode 1006 of the light emitting element. Part of the gate signal line 1003 functions as a gate electrode of the first transistor 1001.

(Embodiment 5)
One mode of a light-emitting device including the light-emitting element of the present invention will be described with reference to FIGS.

  In FIG. 7, a transistor 11 is provided to drive the light emitting element 12 of the present invention. The light-emitting element 12 is a light-emitting element of the present invention having a layer 15 in which at least a composite layer and a layer containing a light-emitting substance are stacked between a first electrode 13 and a second electrode 14. The drain of the transistor 11 and the first electrode 13 are electrically connected by a wiring 17 penetrating the first interlayer insulating films 16a, 16b, and 16c. The light emitting element 12 is separated from another light emitting element provided adjacent thereto by a partition wall layer 18. The light-emitting device of the present invention having such a structure is provided over the substrate 10 in this embodiment.

  Note that the transistor 11 illustrated in FIG. 7 is a top-gate transistor in which a gate electrode is provided on the side opposite to a substrate with a semiconductor layer as a center. However, the structure of the transistor 11 is not particularly limited, and may be, for example, a bottom gate type. In the case of a bottom gate, the semiconductor layer forming a channel may be formed with a protective film (channel protection type), or the semiconductor layer forming the channel may be partially concave ( Channel etch type). In addition, 21 is a gate electrode, 22 is a gate insulating film, 23 is a semiconductor layer.

  Further, the semiconductor layer included in the transistor 11 may be either crystalline or non-crystalline. Moreover, a semi-amorphous etc. may be sufficient.

The semi-amorphous semiconductor is as follows. A semiconductor having an intermediate structure between amorphous and crystalline (including single crystal and polycrystal) and having a third state that is stable in terms of free energy, has a short-range order, and has a lattice distortion. It includes a crystalline region having. Further, at least a part of the region in the film contains crystal grains of 0.5 to 20 nm. The Raman spectrum is shifted to the lower wavenumber side than 520 cm ⁻¹ . In X-ray diffraction, diffraction peaks of (111) and (220) that are derived from the Si crystal lattice are observed. In order to terminate dangling bonds (dangling bonds), hydrogen or halogen is contained at least 1 atomic% or more. It is also called a so-called microcrystalline semiconductor (microcrystal semiconductor). A gas made of silicide is formed by glow discharge decomposition (plasma CVD). As the gas made of silicide, SiH ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , SiF _{4, and the} like can be used. The gas made of silicide may be diluted with H ₂ , or H ₂ and one or more kinds of rare gas elements selected from He, Ar, Kr, and Ne. The dilution rate is in the range of 2 to 1000 times. The pressure is generally in the range of 0.1 Pa to 133 Pa, and the power supply frequency is 1 MHz to 120 MHz, preferably 13 MHz to 60 MHz. The substrate heating temperature may be 300 ° C. or less, preferably 100 to 250 ° C. As an impurity element in the film, impurities of atmospheric components such as oxygen, nitrogen, and carbon are desirably 1 × 10 ²⁰ / cm ³ or less, and in particular, the oxygen concentration is 5 × 10 ¹⁹ / cm ³ or less, preferably 1 × 10 ¹⁹ / cm ³ or less. Note that the mobility of a TFT (thin film transistor) using a semi-amorphous semiconductor is approximately 1 to 10 m ² / Vsec.

  Further, specific examples of the crystalline semiconductor layer include those made of single crystal or polycrystalline silicon, silicon germanium, or the like. These may be formed by laser crystallization, or may be formed by crystallization by a solid phase growth method using nickel or the like, for example.

  Note that in the case where the semiconductor layer is formed of an amorphous material, for example, amorphous silicon, the transistor 11 and other transistors (transistors constituting a circuit for driving the light-emitting element) are all formed of N-channel transistors. It is preferable that the light emitting device have a circuit. Other than that, a light-emitting device having a circuit including any one of an N-channel transistor and a P-channel transistor, or a light-emitting device including a circuit including both transistors may be used.

  Further, the first interlayer insulating film 16a to 16c may be a multilayer as shown in FIGS. 7A to 7C, or may be a single layer. Note that 16a is made of an inorganic material such as silicon oxide or silicon nitride, and 16b is an organic group having a skeleton structure composed of a bond of acrylic or siloxane (silicon (Si) and oxygen (O)) and containing at least hydrogen as a substituent. (For example, an alkyl group or an aromatic hydrocarbon is used. As a substituent, a fluoro group may be used. Alternatively, an organic group containing at least hydrogen and a fluoro group may be used as a substituent.), It is made of a material having self-flatness such as silicon oxide that can be coated and formed. Further, 16c is made of a silicon nitride film containing argon (Ar). In addition, there is no limitation in particular about the substance which comprises each layer, You may use things other than what was described here. Moreover, you may further combine the layer which consists of substances other than these. As described above, the first interlayer insulating film may be formed using both an inorganic material or an organic material, or may be formed of any one of an inorganic film and an organic film.

  The partition layer 18 preferably has a shape in which the radius of curvature continuously changes at the edge portion. The partition layer 18 is formed using acrylic, siloxane, resist, silicon oxide, or the like. The partition wall layer 18 may be formed of any one of an inorganic film and an organic film, or may be formed using both.

  7A and 7C illustrate a configuration in which only the first interlayer insulating film 16a to 16c is provided between the transistor 11 and the light emitting element 12. FIG. FIG. 7B shows a structure in which the first interlayer insulating films 16a and 16b and the second interlayer insulating films 19a and 19b are provided. In the light emitting device shown in FIG. 7B, the first electrode 13 penetrates through the second interlayer insulating films 19 a and 19 b and is connected to the wiring 17.

  Similarly to the first interlayer insulating films 16a to 16c, the second interlayer insulating film 19a and 19b may be a multilayer or a single layer. 19a is made of a self-flattening material such as acrylic, siloxane, or silicon oxide that can be coated and formed. Further, 19b is made of a silicon nitride film containing argon (Ar). In addition, there is no limitation in particular about the substance which comprises each layer, You may use things other than what was described here. Moreover, you may further combine the layer which consists of substances other than these. As described above, the second interlayer insulating films 19a and 19b may be formed using both inorganic or organic materials, or may be formed of any one of an inorganic film and an organic film.

  In the light-emitting element 12, when each of the first electrode and the second electrode is formed using a light-transmitting substance, the first electrode and the second electrode are represented by the white arrows in FIG. Light emission can be extracted from both the electrode 13 side and the second electrode 14 side. In addition, in the case where only the second electrode 14 is formed using a light-transmitting substance, light emission is extracted only from the second electrode 14 side as represented by a white arrow in FIG. 7B. be able to. In this case, it is preferable that the first electrode 13 is made of a material having a high reflectivity, or a film (reflective film) made of a material having a high reflectivity is provided below the first electrode 13. In addition, in the case where only the first electrode 13 is formed using a light-transmitting substance, light emission is extracted only from the first electrode 13 side as represented by a white arrow in FIG. be able to. In this case, it is preferable that the second electrode 14 is made of a highly reflective material, or a reflective film is provided above the second electrode 14.

  In addition, the light emitting element 12 may be one in which the layer 15 is stacked so as to operate when a voltage is applied so that the potential of the second electrode 14 is higher than the potential of the first electrode 13. Alternatively, the layer 15 may be stacked so as to operate when a voltage is applied so that the potential of the second electrode 14 is lower than the potential of the first electrode 13. In the former case, the transistor 11 is an N-channel transistor, and in the latter case, the transistor 11 is a P-channel transistor.

  As described above, in this embodiment mode, an active light-emitting device that controls driving of a light-emitting element using a transistor has been described. In addition to this, a light-emitting element is driven without particularly providing a driving element such as a transistor. A passive light emitting device may be used.

  FIG. 8 is a perspective view of a passive light emitting device manufactured by applying the present invention. In FIG. 8, over a substrate 951, a layer 955 including a layer containing at least a light-emitting substance and a composite layer is provided between an electrode 952 and an electrode 956 that intersect with each other. An end portion of the electrode 952 is covered with an insulating layer 953. A partition layer 954 is provided over the insulating layer 953. The cross section in the short side direction of the partition wall layer 954 has an inverted trapezoidal shape, and the bottom side is shorter than the top side. In this manner, by providing the partition layer 954, defects in the light-emitting element due to static electricity or the like can be prevented. A passive light emitting device can also be driven with low power consumption by including the light emitting element of the present invention that operates at a low driving voltage.

(Embodiment 6)
Since the light-emitting device using the light-emitting element of the present invention as a pixel has few display defects due to the operation failure of the light-emitting element, the display operation is favorable. In addition, it is possible to obtain an electronic device with little misperception of a display image caused by a display defect. In addition, a light-emitting device using the light-emitting element of the present invention as a light source can be favorably illuminated with few defects due to malfunction of the light-emitting element. By using such a light-emitting device as an illuminating unit such as a backlight, an operation failure in which a dark part is locally formed due to a defect of the light-emitting element is reduced.

  One embodiment of an electronic device mounted with a light emitting device to which the present invention is applied is shown in FIG.

  FIG. 9A illustrates a personal computer manufactured by applying the present invention, which includes a main body 5521, a housing 5522, a display portion 5523, a keyboard 5524, and the like. A personal computer can be completed by incorporating a light emitting device as shown in FIG. 7 as a display portion. Further, a personal computer can be completed even if a light emitting device using the light emitting element of the present invention as a light source is incorporated as a backlight. Specifically, as illustrated in FIG. 10, a liquid crystal device 5512 and a light-emitting device 5513 as a light source may be incorporated between a housing 5511 and a housing 5514. A light-emitting device 5513 includes an array 5518 and a light guide plate 5517 which are formed using the light-emitting elements of the present invention. In FIG. 10, an external input terminal 5515 is attached to the liquid crystal device 5512, and an external input terminal 5516 is attached to the array 5518.

  FIG. 9B illustrates a telephone manufactured by applying the present invention. A main body 5552 includes a display portion 5551, an audio output portion 5554, an audio input portion 5555, an operation switch 5556, an operation switch 5557, an antenna 5553, and the like. It is configured. A telephone can be completed by incorporating a light-emitting device having the light-emitting element of the present invention as a display portion.

  FIG. 9C illustrates a television set manufactured by applying the present invention, which includes a display portion 5531, a housing 5532, a speaker 5533, and the like. A television receiver can be completed by incorporating a light-emitting device having the light-emitting element of the present invention as a display portion.

  As described above, the light-emitting device of the present invention is very suitable for use as a display portion of various electronic devices. Note that the electronic device is not limited to that described in this embodiment, and may be another electronic device such as a navigation device.

(Embodiment 7)
In this embodiment mode, a composite used as a material for the light-emitting element of the present invention is described. The complex is a mixture of one of the conjugated molecules represented by the following general formulas [Chemical Formula 1] to [Chemical Formula 5] and a substance having an electron accepting property with respect to the conjugated molecule.

（式中、ＸとＺは同一または異なっており、且つ、ＸとＺはそれぞれ硫黄原子、酸素原子、水素、アルキル基もしくはアリール基が結合した窒素原子、又は水素、アルキル基もしくはアリール基が結合した珪素原子のいずれかであり、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかである。）

(Wherein X and Z are the same or different, and X and Z are each a nitrogen atom to which a sulfur atom, oxygen atom, hydrogen, alkyl group or aryl group is bonded, or a hydrogen, alkyl group or aryl group bonded thereto) Y is an arylene group, and R ¹ to R ⁶ are each a hydrogen atom, an aryl group, an alkyl group, a cyano group, a dialkylamino group, a thioalkoxy group, or an alkoxy group. is there.)

（式中、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかである。）

(In the formula, Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, a thioalkoxy group, or an alkoxy group.)

（式中、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかである。）

(In the formula, Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, a thioalkoxy group, or an alkoxy group.)

（式中、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかであり、Ｒ^７とＲ^８は水素、アルキル基又はアリール基のいずれかである。）

(Wherein Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, aryl group, alkyl group, cyano group, dialkylamino group, thioalkoxy group, or alkoxy group, and R ⁷ and R ⁸ is either hydrogen, an alkyl group or an aryl group.)

（式中、Ｙはアリーレン基であり、Ｒ^１からＲ^６はそれぞれ、水素、アリール基、アルキル基、シアノ基、ジアルキルアミノ基、チオアルコキシ基、又はアルコキシ基のいずれかであり、Ｒ^７からＲ^１０はそれぞれ、水素、アルキル基又はアリール基のいずれかである。）

(In the formula, Y is an arylene group, each R ⁶ is from R ^1, hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, or a thioalkoxy group, or an alkoxy group, a R ⁷ Each R ¹⁰ is hydrogen, an alkyl group, or an aryl group.)

  In the conjugated molecules represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5], Y is an arylene group and a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or oxygen, nitrogen , A divalent heteroaromatic group having 4 to 30 carbon atoms and containing sulfur or silicon.

  Since these conjugated molecules have a very low ionization potential, electrons are exchanged inside the complex by forming a complex with the electron accepting substance. Therefore, a composite layer made of a composite has a feature that holes are generated or holes are easy to move. In addition, due to such characteristics, the composite layer also has a characteristic of high conductivity. Therefore, when a layer composed of a material having a low ionization potential is compared with the composite layer, the composite layer has an electron-accepting substance and therefore has a better hole flow.

  As the electron accepting substance, a metal oxide or a metal nitride is preferable. Among them, the transition metal oxide of any of Groups 4 to 12 of the periodic table has high electron acceptability. Further, many transition metal oxides of Groups 4 to 8 of the periodic table have a higher electron accepting property. In particular, vanadium oxide, molybdenum oxide, rhenium oxide, tungsten oxide, ruthenium oxide, titanium oxide, chromium oxide, zirconium oxide, hafnium oxide, tantalum oxide, and niobium oxide are preferable.

Further, an organic compound having an electron accepting property may be used as the electron accepting substance. Specific examples include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (F4-TCNQ) and chloranil. Further, a Lewis acid may be used as the electron accepting substance. Examples of Lewis acid include FeCl ₃ (iron chloride (III)) and AlCl ₃ (aluminum chloride).

  In addition, the optimum mixing ratio of the electron-accepting substance in the composite layer and any of the conjugated molecules represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5] is as follows. -10, preferably 0.5-2. At this mixing ratio, electrons are efficiently exchanged between the electron-accepting substance and the conjugated molecule, and the conductivity of the composite layer is the highest.

In this example, as a representative of the compound represented by the general formula [Chemical Formula 2], 1,4-di (3,4-ethylenedioxy-2-thienyl) benzene represented by the following formula [Chemical Formula 6] and the following formula: Each of 4,4′-di (3,4-ethylenedioxy-2-thienyl) biphenyl represented by [Chemical Formula 7] was synthesized.

Compounds [Chemical 6] and [Chemical 7] have very low ionization potential. That is, in the compounds represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5], R ¹ and R ² form a ring structure, and R ³ and R ⁴ form a ring structure, thereby effectively conjugating the whole molecule. It turns out that the length extends.

FIG. 11 shows 1,4-di (3,4-ethylenedioxy-2-thienyl) benzene ([Chem. 6]) and its analog 1,4-bis (3,4-dihexyloxy-2- It is an ultraviolet-visible absorption spectrum of thienyl) benzene. The structure of 1,4-bis (3,4-dihexyloxy-2-thienyl) benzene is shown in [Chemical Formula 8]. As shown in FIG. 11 (A), the former absorption maximum is observed at 380 nm, whereas as shown in FIG. 11 (B), the latter is observed at 300 nm. It can be seen that it has a more extended conjugated system. As shown in FIG. 11A, the absorption intensity in the visible light region of [Chemical Formula 6] is very small, which is a significant difference from the conventional hole injection material.

  Furthermore, cyclic voltammetry was measured with [Chemical Formula 6] and [Chemical Formula 8]. This measurement result also showed that [Chemical 6] has a more extended conjugated system. Cyclic voltammetry was measured using acetonitrile as a solvent and tetrabutylammonium perchlorate as a supporting electrolyte. The working electrode as well as the counter electrode is platinum. The reference electrode was silver / silver chloride.

As a result, the oxidation potential of [Chemical 6] is 1.20 V (vs. Ag ^/ Ag ⁺ ), whereas the oxidation potential of [Chemical 8] is 1.68 V, and [Chemical 8] is more difficult to oxidize. I understood that.

That is, in a conjugated molecule represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5], when a ring structure is formed by R ¹ and R ² and a ring structure is formed by R ³ and R ⁴ , the entire molecule is effective. The conjugate length is extended. As the effective conjugate length increases, the band gap decreases and the ionization potential decreases. Therefore, the electron donating property of the conjugated molecule is further increased. Therefore, by forming a composite layer using a conjugated molecule having an extended effective conjugate length and an electron-accepting substance, a composite layer having a higher conductivity can be obtained because holes are more easily generated.

In this example, as a representative of the compound represented by the general formula [Chemical Formula 2], 1,4-di (3,4-ethylenedioxy-5-trimethylsilyl-2-thienyl) represented by the following Formula [Chemical Formula 9] The synthesis of benzene is described.

A synthesis scheme is shown in FIG. A dry THF solution (100 mL) of 3,4-ethylenedioxythiophene (compound of FIG. 12 (A), 10.30 g, 72.5 mmol) in a hexane solution of 1.56N n-butyllithium (48 mL, 74.9 mmol). ) Was added dropwise at -78 ° C. After completion of dropping, the mixture was stirred at -78 ° C for 1 hour. Chlorotrimethylsilane (8.93 g, 82.3 mmol) was added dropwise to this solution, and then the reaction solution was gradually warmed to room temperature. After stirring for 3 hours, the reaction mixture was concentrated under reduced pressure and then extracted with hexane. The hexane layer was dried over magnesium sulfate and then filtered. The filtrate was concentrated and the residue was distilled under reduced pressure (200 Pa, 94-100 ° C.) to obtain the compound shown in FIG. 12B, 2-trimethylsilyl-3,4-ethylenedioxythiophene. Yield 84%. ¹ H NMR (300 MHz, CDCl ₃ ) δ 0.286 (s, 9H), 4.16 (s, 2H), 4.17 (s, 2H), 6.54 (s, 1H): ¹³ C NMR ( 75 MHz, CDCl ₃ ) δ −0.74, 64.42, 64.51, 104.68, 111.28, 142.63, 147.25.

To a compound shown in FIG. 12B, 2-trimethylsilyl-3,4-ethylenedioxythiophene (18.6 g, 86.0 mmol) in dry THF (150 mL) at −78 ° C., 1.56 N n- Butyllithium in hexane (55 mL, 86.0 mmol) was added dropwise. After completion of the dropwise addition, the mixture was stirred at -78 ° C for 1 hour and at 0 ° C for 30 minutes. This solution was added dropwise at room temperature to a dry THF suspension (100 mL) of zinc chloride (11.69 g, 85.8 mmol). Thereafter, the mixture was stirred for 1 hour to obtain the compound represented by FIG. Thereafter, 1,4-dibromobenzene (6.759 g, 28.7 mmol) and tetrakistriphenylphosphine palladium (0) (1.28 g, 1.11 mmol) were added, and the mixture was further heated to reflux for 10 hours. The reaction mixture was poured into about 1 L of water, and the precipitate was filtered. The filtrate is dried, purified by silica gel column chromatography (developing solution, hexane / ethyl acetate 10/1 to 2/1), and further recrystallized with hexane / ethyl acetate (5/1). The compound represented by 12 (D), 1,4-di (3,4-ethylenedioxy-5-trimethylsilyl-2-thienyl) benzene, was obtained. Yield 43%. ¹ H NMR (300 MHz, CDCl ₃ ) δ 0.311 (s, 18H), 4.27 (s, 4H), 4.29 (s, 4H), 7.69 (s, 4H).

  FIG. 13 shows an ultraviolet-visible absorption spectrum of the synthesized compound represented by FIG. As shown in FIG. 13, the absorption in the visible light region is extremely small, and the coloring of the element can be greatly reduced due to this.

In this example, effects of introducing a substituent other than hydrogen into R ⁵ and R ⁶ in the compounds represented by the general formulas [Chemical Formula 1] to [Chemical Formula 5] will be described. When R ⁵ and R ⁶ are hydrogen, the solubility is very low. For example, the compound represented by the formula [Chemical Formula 6] shown in Example 1 has a solubility in chloroform of less than 1 wt% at 25 ° C. In contrast, when R ⁵ and R ⁶ are trimethylsilyl groups as shown in FIG. 12D, the solubility in chloroform at 25 ° C. is 15.4 wt%. Thus, the solubility can be remarkably improved by introducing substituents other than hydrogen into R ⁵ and R ⁶ .

Further, when hydrogen is introduced into R ⁵ and R ⁶ , the solubility is low. However, when a substituent other than hydrogen is introduced, a deposited film with good film quality is obtained reflecting high solubility.

In this example, as a representative of the compound represented by the general formula [Chemical Formula 2], 4,4′-bis (5-phenyl-3,4-ethylenedioxy-2-thienyl represented by the following Formula [Chemical Formula 10] ) Synthesis of biphenyl (hereinafter referred to as DPEBP) will be described.

First, the synthesis of the following formula [Formula 11] (hereinafter referred to as intermediate a) is described. 250 ml of dry THF was added to 22.41 g of 2,3-dihydrothieno- [3,4-b] -1,4-dioxin and cooled to -78 ° C. 100 ml of n-butyllithium (1.58 M hexane solution) was added dropwise and stirred for 1 hour. The obtained mixture was added to 25.84 g of zinc chloride at room temperature, and further stirred at room temperature for 1 hour. To this were added 18.3 ml of bromobenzene and 1.83 g of tetrakistriphenylphosphine palladium, and the mixture was stirred for 5 hours with heating under reflux. Ethyl acetate, 1M hydrochloric acid and water were added to the solution cooled to room temperature, and the organic layer was separated. After drying with magnesium sulfate, the solvent was concentrated. Purified by column chromatography (hexane / ethyl acetate). NMR data is shown below. ¹ H NMR (CDCl ₃ , δ) 7.72 ppm (d, 2H), 7.36 ppm (t, 2H), 7.21 ppm (t, 1H), 6.29 ppm (s, 1H), 4.29 ppm (m 4H).

Next, 100 ml of THF was added to 10.36 g of the intermediate a obtained above and cooled to -78 ° C. 33.1 ml of n-butyllithium (1.58 M hexane solution) was added dropwise and stirred for 1 hour. The obtained mixture was added to 7.77 g of zinc chloride at room temperature, and further stirred at room temperature for 1 hour. To this, 8.77 g of 4,4′-diiodobiphenyl and 549 mg of tetrakistriphenylphosphine palladium were added and stirred for 5 hours while heating under reflux. The solid obtained by filtering this was washed with ethanol. Recrystallization was performed with chloroform to obtain an organic compound DPEBP of the present invention (yellow powder). NMR data is shown below. ¹ H NMR (CDCl ₃ , δ) 7.77 ppm (m, 12H), 7.44 ppm (t, 4H), 7.28 ppm (t, 2H), 4.45 ppm (s, 8H).

In this example, as a representative of the compound represented by the general formula [Chemical Formula 2], 1,4-bis (5-phenyl-3,4-ethylenedioxy-2-thienyl) represented by the following Formula [Chemical Formula 12] The synthesis of benzene (hereinafter referred to as DPEBZ) will be described.

To 6.07 g of the intermediate a obtained in Example 4, 100 ml of THF was added and cooled to -78 ° C. 19.4 ml of n-butyllithium (1.58 M hexane solution) was added dropwise and stirred for 1 hour. The obtained mixture was added to 4.50 g of zinc chloride at room temperature, and the mixture was further stirred at room temperature for 1 hour. To this, 4.12 g of 1,4-diiodobenzene and 321 mg of tetrakistriphenylphosphine palladium were added and stirred for 5 hours while heating under reflux. The solid obtained by filtering this was washed with ethanol. Recrystallization was performed with chloroform to obtain an organic compound DPEBZ of the present invention (orange powder). NMR data is shown below. ¹ H NMR (CDCl ₃ , δ) 7.77 ppm (m, 8H), 7.38 ppm (t, 4H), 7.23 ppm (t, 2H), 4.38 ppm (s, 8H).

In this example, as a representative of the compound represented by the general formula [Chemical Formula 2], 4,4′-bis [5- (4-tert-butylphenyl) -3,4- The synthesis of ethylenedioxy-2-thienyl) biphenyl (hereinafter referred to as DtBuPEBP) will be described.

First, the synthesis of the following formula [Formula 14] (hereinafter referred to as intermediate b), which is an intermediate, will be described. First, 100 ml of THF was added to 10.57 g of 2,3-dihydrothieno- [3,4-b] -1,4-dioxin and cooled to -78 ° C. 37.2 ml of LDA (2.0M) was added dropwise and stirred for 1 hour. 12.14 g of zinc chloride was added, and the mixture was further stirred at room temperature for 1 hour. To this, 14.3 ml of 1-bromo-4-tert-butylbenzene and 859 mg of tetrakistriphenylphosphine palladium were added, and the mixture was stirred for 8 hours with heating under reflux. Ethyl acetate and water were added to the solution cooled to room temperature, and the organic layer was separated. After drying with magnesium sulfate, the solvent was concentrated. Then, it was purified by column chromatography (toluene). NMR data is shown below. ¹ H NMR (CDCl ₃ , δ) 7.67 ppm (d, 2H), 7.45 ppm (d, 2H), 6.32 ppm (s, 1H), 1.40 ppm (s, 9H).

Next, 50 ml of THF was added to 2.56 g of the intermediate b obtained above, and the mixture was cooled to −78 ° C. LDA (2.0 M) 5.12 ml was added dropwise and stirred for 1 hour. Zinc chloride (1.53 g) was added, and the mixture was further stirred at room temperature for 1 hour. To this, 1.71 g of 4,4′-diiodobiphenyl and 107 mg of tetrakistriphenylphosphine palladium were added and stirred for 6 hours under heating and reflux. Ethyl acetate, 1M hydrochloric acid and water were added to the solution cooled to room temperature, and the organic layer was separated. After drying with magnesium sulfate, the solvent was concentrated. Recrystallization was performed with chloroform to obtain an organic compound DtBuPEBP of the present invention. NMR data is shown below. ¹ H NMR (CDCl ₃ , δ) 7.80 ppm (d, 4H), 7.66 ppm (m, 8H), 7.41 ppm (d, 4H), 4.36 ppm (s, 8H), 1.32 ppm (s) 9H).

FIG. 6 illustrates a light-emitting element of the present invention. FIG. 6 illustrates a light-emitting element of the present invention. FIG. 6 illustrates a light-emitting element of the present invention. FIG. 6 is a top view of a light-emitting device. The figure showing the circuit for operating one pixel. The top view in a pixel part. FIG. 6 illustrates a light-emitting element of the present invention. FIG. 6 illustrates a passive light-emitting device of the present invention. FIG. 16 illustrates an electronic device of the invention. FIG. 11 illustrates an electronic device in which a light-emitting element of the present invention is incorporated in a backlight. The figure which shows the ultraviolet-visible spectrum of a conjugated molecule. Synthesis scheme diagram. The figure which shows the ultraviolet-visible spectrum (2.55 * 10 <^-5> M in a methylene chloride) of a conjugated molecule. The figure which shows a prior art example.

Explanation of symbols

101 first electrode 102 second electrode 111 first layer 112 second layer 113 third layer 114 composite layer 115 hole transport layer 116 composite layer 117 hole injection layer 118 composite layer 201 first electrode 202 Second electrode 211 First layer 212 Second layer 213 Third layer 214 Composite layer 215 Electron generation layer 301 First electrode 302 Second electrode 311 First layer 312 Second layer 313 Third layer Layer 324 first composite layer 325 electron generation layer 326 hole transport layer 327 second composite layer 328 second composite layer 329 hole injection layer 330 second composite layer 6500 substrate 6503 FPC
6504 Printed Wiring Board (PWB)
6511 Pixel portion 6512 Source signal line driving circuit 6513 Writing gate signal line driving circuit 6514 Erasing gate signal line driving circuit 901 First transistor 902 Second transistor 903 Light emitting element 911 Gate signal line 912 Source signal line 913 Writing Gate signal line driving circuit 914 erasing gate signal line driving circuit 915 source signal line driving circuit 916 power supply 917 current supply line 918 switch 919 switch 920 switch 1001 first transistor 1002 second transistor 1003 gate signal line 1004 source signal line 1005 Current supply line 1006 Electrode 10 Substrate 11 Transistor 12 Light emitting element 13 First electrode 14 Second electrode 15 Layer 16a First interlayer insulating film 16b First interlayer insulating film 16c First interlayer insulating film 17 Wiring 18 Partition layer 19a Two-layer insulating film 19b Second interlayer insulating film 21 Gate electrode 22 Gate insulating film 23 Semiconductor layer 951 Substrate 952 Electrode 953 Insulating layer 954 Partition layer 955 Layer 956 Electrode 5521 Main body 5522 Housing 5523 Display unit 5524 Keyboard 5551 Display unit 5552 Main unit 5553 Antenna 5554 Audio output unit 5555 Audio input unit 5556 Operation switch 5557 Operation switch 5531 Display unit 5532 Case 5533 Speaker 5511 Case 5512 Liquid crystal device 5513 Light emitting device 5514 Case 5515 External input terminal 5516 External input terminal 5517 Light guide plate 5518 Array 1501 First 1 electrode 1502 second electrode 1503 layer 1511 hole transport layer 1512 light emitting layer 1513 electron transport layer

Claims (9)

A pair of electrodes composed of a first electrode and a second electrode;
A light emitting layer between the pair of electrodes;
A composite layer disposed between the light emitting layer and at least one of the pair of electrodes;
The composite layer is a layer formed of a composite of a conjugated molecule represented by any one of the general formulas [Chemical Formula 1] to [Chemical Formula 5] and a substance having an electron accepting property with respect to the conjugated molecule. .

(Wherein X and Z are the same or different, and X and Z are each a nitrogen atom to which a sulfur atom, oxygen atom, hydrogen, alkyl group or aryl group is bonded, or a hydrogen, alkyl group or aryl group bonded thereto) Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, a thioalkoxy group, or an alkoxy group.)

(In the formula, Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, a thioalkoxy group, or an alkoxy group.)

(In the formula, Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, a thioalkoxy group, or an alkoxy group.)

(Wherein Y is an arylene group, and R ¹ to R ⁶ are each hydrogen, aryl group, alkyl group, cyano group, dialkylamino group, thioalkoxy group, or alkoxy group, and R ⁷ and Each R ⁸ is hydrogen, an alkyl group, or an aryl group.)

(In the formula, Y is an arylene group, each R ⁶ is from R ^1, hydrogen, an aryl group, an alkyl group, a cyano group, a dialkylamino group, or a thioalkoxy group, or an alkoxy group, a R ⁷ Each R ¹⁰ is hydrogen, an alkyl group, or an aryl group.)   The light-emitting element emits light from the light-emitting layer when a voltage is applied so that the potential of the first electrode is higher than the potential of the second electrode. The light emitting element, wherein the composite layer is disposed between the light emitting layer and the light emitting layer.   The light-emitting element emits light from the light-emitting layer when a voltage is applied so that the potential of the first electrode is higher than the potential of the second electrode. The composite layer is disposed between the light emitting layer and an electron generating layer in contact with the composite layer on the light emitting layer side. The light-emitting element emits light from the light-emitting layer when a voltage is applied so that the potential of the first electrode is higher than the potential of the second electrode.
The composite layer is disposed between each of the first electrode and the light emitting layer and between the second electrode and the light emitting layer,
A light-emitting element, comprising: an electron generation layer that is in contact with the composite layer disposed between the second electrode and the light-emitting layer on the light-emitting layer side.   5. The light-emitting element according to claim 1, wherein the substance having an electron accepting property with respect to the conjugated molecule is a metal oxide, a metal nitride, an organic compound, or a Lewis acid. .   6. The conjugated molecule according to claim 1, wherein Y is a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or a carbon number containing oxygen, nitrogen, sulfur, or silicon. A light-emitting element having 4 to 30 divalent heteroaromatic groups. The light emission according to any one of claims 1 to 6, wherein R ¹ and R ² of the conjugated molecule form a ring structure, and R ³ and R ⁴ form a ring structure. element.   An electronic apparatus using the light-emitting element according to claim 1 as a pixel.   An electronic apparatus using the light-emitting element according to claim 1 as a light source.

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